#define TEMPLATE_BF_SIZE 8
+/**
+ * How many bytes should a bloomfilter be if we have already seen
+ * entry_count responses? Note that #GNUNET_CONSTANTS_BLOOMFILTER_K
+ * gives us the number of bits set per entry. Furthermore, we should
+ * not re-size the filter too often (to keep it cheap).
+ *
+ * Since other peers will also add entries but not resize the filter,
+ * we should generally pick a slightly larger size than what the
+ * strict math would suggest.
+ *
+ * @param entry_count expected number of entries in the Bloom filter
+ * @return must be a power of two and smaller or equal to 2^15.
+ */
+static size_t
+compute_bloomfilter_size (unsigned int entry_count)
+{
+ size_t size;
+ unsigned int ideal = (entry_count * BLOOMFILTER_K) / 4;
+ uint16_t max = 1 << 15;
+
+ if (entry_count > max)
+ return max;
+ size = 8;
+ while ((size < max) && (size < ideal))
+ size *= 2;
+ if (size > max)
+ return max;
+ return size;
+}
+
+
/**
* Create a new block group.
*
size_t raw_data_size,
va_list va)
{
+ unsigned int bf_size;
+ const char *guard;
+
+ guard = va_arg (va, const char *);
+ if (0 == memcmp (guard,
+ "seen-set-size",
+ strlen ("seen-set-size")))
+ bf_size = compute_bloomfilter_size (va_arg (va, unsigned int));
+ else if (0 == memcmp (guard,
+ "filter-size",
+ strlen ("filter-size")))
+ bf_size = va_arg (va, unsigned int);
+ else
+ {
+ GNUNET_break (0);
+ bf_size = TEMPLATE_BF_SIZE;
+ }
+ GNUNET_break (NULL == va_arg (va, const char *));
return GNUNET_BLOCK_GROUP_bf_create (cls,
TEMPLATE_BF_SIZE,
BLOOMFILTER_K,